How much practicing do you do?

As I advance through the course I find myself forgetting quite a bit of what I have learned earlier on, even if it was a topic I was studying last week! I am curious to know how much time you spend revisiting old topics?
Personally speaking I find I would rather spend time on the new topic as it brings my goal of getting a gold completed tree closer!

I have now completed the tree, but I really took my time going down the tree.
In the beginning, when it was easier, I did like 40XP practice, 10XP new lesson per day.
Later, it was mostly practice, with a new lesson only once or twice a week, or when I felt like the practice was too easy for me and I did not do any mistakes in practice.
Take your time, do not rush it, or you will remember nothing.
It's quite possible to fly trough the tree in a month or two, but after another month, you remember nothing.

Well, I get bored pretty easily. So... I use the app on the phone while pooping or whenever I'm waiting at the bus stop and sometimes (if I'm not too tired that night) I visit the website on my computer when I'm back home.

I often just revisit old skills every few days, I've been practicing my Spanish lately so Japanese practice has been a bit slow. But a method I often use is writing down a list of words (and particles, kanji, etc. if you need practice with those) and practice using them in context. I find context is supppppper important to help me remember the words better! I find it especially useful for names and places: 富士山は大きいですよ！富士山は可愛いですね～、富士山は嬉しいです。The core word here? 富士山(ふじさん)！Aka Mt. Fuji. Will never forget it now due to all the sentence repetition :).

Side note: I basically review and study new stuff throughout the day whenever I have the time.

I practice a skill until I think I know it well enough to take in new information before I try the next thing and if it's too much I take a step back. Sometimes my brain just needs some time to figure out how to store the new information long term. I practice every day and make sure to at least reinforce what I already know.
I take notes on words I have trouble with or that Duo doesn't bring up often enough (like きたない that I've only seen in the first hiragana lessons).

I've also dropped Japanese more times than I can count since I started learning it a few years ago, but every time I come back and redo the course it's a little easier, but I'd recommend never forgetting in the first place, just don't bite off more than your brain can chew.

If by "the basics" you mean hiragana, Duolingo isn't a good place to learn that. I used the apps "Hiragana Learn Experiment" and "Katakana Learn Experiment" to memorize hiragana and katakana respectively. It took a lot of practice, but I think it was worth it.

If you mean the vocabulary, all I can really say is you need to practice. And try not to beat yourself up about not getting it right away. Nobody does. It takes time.

If you mean kanji (the more complicated and inconsistently pronounced characters), I find https://jisho.org/ helps to understand and memorize them. You can copy+paste kanji and search to find meaning and readings and stroke order (how to write them, this is more important than it sounds).

Notes on kanji:

Reading: kanji have different "readings" in different words. There are "kun-readings" and "on-readings" which are (respectively) native Japanese pronunciations and approximations of foreign pronunciations using Japanese sounds. That doesn't really matter, but it might make things less confusing on Jisho.

Stroke order: all the Japanese characters (kanji, hiragana, katakana) have a specific order in which to draw every part of them. As long as you're not writing anything by hand, it's not something you need to learn, but I find it helps a great deal with memorizing what the character looks like so I can distinguish between similar ones.

Radicals: kanji can look like an intricate random mess, but there's a method to the madness and its name is radicals. They're a set of parts you can put together in different ways to make different kanji. For example: the kanji 時 (time/hour) is made up of 日 (sun/day), 土 (earth/ground), and 寸 (measurement/small), which are all their own kanji as well.
Okay, maybe not a great explanation, but think of it like our letters: the English word "time" contains Tim, I and me, which all have their own meaning. Okay now imagine every letter sort of had its own meaning, though the words they make together don't always make sense (no idea why you need earth to make time, for example)... I don't know, I don't fully understand it myself.

Well, maybe I'm just thinking it in a western way (in my language there is not distinction between planet/ground/soil), but from ancient ages time was understood with the measurement of the sun position relative to the ground/earth

I'm still new, but I am using a technique that, every day I used 50XP of practice, then start an entirely new lesson till completion (or 50XP), then practice for 50XP again. Feeling motivated? Continue practicing again once or twice, but not adding another lesson as I need to boil down the lesson I learned in the beginning.